Field of the Invention
The invention relates to a method for allocating a radio channel in a radio communications system. The radio communications system uses radio channels, which are in each case formed by at least one timeslot for transmitting information. The invention further relates to a corresponding radio communications system.
The allocation of radio channels to mobile stations in a radio communications system is normally carried out by radio stations which supply radio resources to the mobile stations or radio subscribers in their associated radio cells. The information is transmitted, via a radio interface, on the allocated radio channel, which is in each case formed by at least one timeslot. Channel allocation problems occur whenever interference occurs among the mobile stations and/or the radio stations, or between a mobile station and a radio station. Particularly in the case of radio communications systems having a frequency repetition interval (reuse cluster) equal to unity, the high interference level means that a soft handover, that is to say connection relaying, is required, in which the mobile stations or radio subscribers at cell boundaries must be supplied with radio resources simultaneously from at least two radio stations. This results in radio stations being networked with one another and results in a considerable additional signaling complexity. Furthermore, the overall capacity of the radio communications system is reduced by subscribers or mobile stations who or which remain in such a soft-handover area.
Published European Patent Application EP 0 411 878 A2 discloses a configuration for managing the power control for radio channels in a radio communications system having a number of base stations and mobile stations. In this case, the radio channels are each allocated an individual transmission/reception power level as a function of the prevailing transmission conditions.
Published British Patent Application GB 2 288 517 A discloses a radio communications system, in which the interference levels of the radio channels are monitored, and are compared with a reference level. A new channel is then chosen if this channel has a level which is lower than the reference level.
A method for a dynamic allocation of transmission channels under different conditions in a communications system is described in the article "Distributed Measurement-based Dynamic Channel Assignment for Personal Communications", IEEE, volume 2, No. CONF.45, Jul. 25, 1995. An allocation algorithm is proposed, which operates on the principle of a least possible interference.